1. Field of the Invention
This invention generally concerns a power train for transmitting power from an internal combustion engine to a rotating cutting blade and particularly relates to a double reduction power transmission system using a combination of toothed and toothless pulleys respectively coacting with toothed and toothless transmission belts for driving high horsepower cutting machinery.
2. Description of Prior Developments
Self-propelled concrete saws are well knosn and have been used for many years. Heretofore, such self-propelled saws have used a system of v-belts and friction pulleys for transmitting power directly from a prime mover to a cutting blade drive shaft. An example of such an apparatus is disclosed in U.S. Pat. No. 3,417,638, which is incorporated herein by reference.
The current demand for greater cutting rates has necessitated the transmission of greater power from a prime mover to a cutting blade through a conventional power train. However, known pulley and belt systems designed for lower power transmission slip and/or break under higher loads. In the past, the solution to this problem has been to add additional pulleys and v-belts to the engine power takeoff shaft and to the blade drive shaft in order to distribute the greater power over more belts and pulleys.
However, as more and more pulleys and belts are added, the amount of power transmitted to the blade shaft does not increase proportionally and a condition of "diminishing returns" results. Moreover, space considerations often preclude the use of numerous pulleys and belts. This space problem has been overcome through the use of larger diameter pulleys which improve the ability of each v-belt to transmit power through greater contact arcs on each coacting pulley.
The use of larger pulleys frequently created another problem. Since such pulleys are typically mounted on the same shaft upon which the cutting blade is mounted, the useful cutting depth of the blade would be decreased due to the outer diameter of the pulley contacting the surface being cut.
Moreover, by mounting a larger pulley on the power takeoff shaft of the engine, the operating speed of the engine had to be reduced in order to run the cutting blade at a preferred speed. This condition often resulted in the engine running within inefficient low speed and low horsepower ranges. While a gear and chain drive would significantly reduce the pulley pavement interference problem through the mounting of a smaller diameter gear on the blade shaft, chains are poorly suited to high speed applications such as those intended to be carried out by the present invention. At high speeds, chains have been known to break apart thereby creating an extremely dangerous condition.
Accordingly, a need has risen for a power transmission system capable of safely and efficiently transmitting power in the range of 100 horsepower from a prime mover to a drive shaft for driving a cutter blade.